Problem is, I'm having a hard time finding nondairy yogurt under valid kosher certification. It occurred to me that I can probably do something with Tofutti Sour Supreme, vanilla extract, and agave/sugar, but I'm a little hazy on the proportions.

Any suggestions? If there's a better substitution, I'm open, but I've been checking a few stores in the area for any kind of kosher soygurt (or other non-dairy equivalent) and come up empty.